Mufflers with side branch tuning chambers



y 1968 J. c. WALKER ET AL 3,382,948

MUFFLERS WITH SIDE BRANCH TUNTNG CHAMBERS 2 Sheets-Sheet l Original Filed Oct. 30 1963 mus/st y 1963 J. c. WALKER ET AL 3,382,948

MUFFLERS WITH SIDE BRANCH TUNING CHAMBERS 2 Sheets-Sheet Original Filed Oct. 30, 1963 m a 72' C at fifefziyaff W?" axm/z/s United States Patent 3,382,948 MUFFLERS WITH SIDE BRAWCH TUNING CHAMBERS John C. Walker and Paul F. Jettinghotf, Jackson, Mich.,

assignors to Walker Manufacturing Company, a corporation of Delaware Continuation of application Ser. No. 320,212, Oct. 30, 1963. This application Oct. 13, 1965, Ser. No. 505,097 2 Claims. (Cl. 181-48) ABSTRACT OF THE DISCLOSURE A dual exhaust system for a V-type engine comprised of two separate individual systems. Each system comprises three units, one of which silences high frequency sounds, the second of which attenuates a broad band of high frequency sounds, intermediate frequencies and a selected low frequency, and a third unit that attenuates a higher frequency than the second unit as well as other high frequencies. The insertion of the units into the length of pipe and particularly the insertion of the second and third units results in the formation of a resonant frequency for the system which is so formed that the antinodes of the respective frequencies silenced by the second and third units occur at these units.

This invention relates to exhaust systems for automotive vehicles and is a continuation of our copending patent application Ser. No. 320,212, filed Oct. 30, 1963, now abandoned.

It is an object of this invention to provide a multi-part exhaust system containing a multiplicity of silencing components which are designed and arranged so as to silence effectively the whole spectrum of exhaust gas sound amanating from an automotive engine.

It is another object of this invention to provide an exhaust system that is small in diameter and, therefore, takes a minimum of space beneath the body of an automotive vehicle.

A further object of the invention is to provide an exhaust system which has a minimum back pressure and in which the silencing components are distributed over the entire length of the system.

A further and particular object of the invention is to provide a dual, multi-part exhaust system for V-8 automotive engines.

The invention accomplishes the foregoing and other objects by means of a construction in which each side of the dual exhaust system comprises three silencing com ponents. One of these is a spit chamber assembly for removing high frequency noises. An intermediate unit is preferably located as close as possible to the anti-node of the 3rd harmonic of the fundamental pipe resonant frequency of the complete side of the system including the three silencing components and the interconnecting pipe sectios and is designed to attenuate this 3rd harmonic as well as a relatively broad band of high and intermediate frequencies and roughness. The last unit of each dual section is a tuning chamber that is tuned to attenuate a higher objectionable pipe resonant frequency, typically the th harmonic of the fundamental pipe frequency. The last unit is located upstream from the end of the system and as close as possible to an anti-node of the 5th harmonic of the exhaust pipe system which, as has been previously noted, is comprised of three components and the respective interconnecting pipe sections. Preferably, laminated construction is used, as indicated hereinafter, and optimum results are obtained when certain types of louvers are used, as will be hereinafter described.

The invention is illustrated in the accompanying drawings in which:

FIGURE 1 is a schematic perspectiveview, partly in phantom, of the dual exhaust system of this invention;

FIGURE 2 is a side elevation, partly in section, of the first portion of one section of the dual exhaust system;

FIGURE 2A is a cross-section along line 2A2A of FIGURE 2;

FIGURE 3 is a cross-section through the louvers used in the spit chamber assembly of FIGURE 2;

FIGURE 4 is a view, taken at right angles to FIG- URE 3;

FIGURE 5 is a longitudinal section through the intermediate portion of the exhaust system;

FIGURE 6 is an end view of the silencing component shown in FIGURE 5, as taken from the left-hand end;

FIGURE 7 is a longitudinal cross-section through the third and last silencing component of the dual system;

FIGURE 8 is a cross-section along the line 8-8 of FIGURE 7;

FIGURE 9 is a developed layout, in section, of the louvers used in the components of FIGURE 7;

FIGURE 10 is a side elevation of the louvers shown in FIGURE 9.

Turning now to FIGURE 1 of the drawings, there is a V-8 engine 1 which has an exhaust silencing system that consists of left and right-hand sections 3 and 5, that is, it is a dual exhaust system. Since the components in each section 3 and 5 are substantially identical, a detailed description will be given hereinafter of only one of the sections and similar reference numbers will be used to indicate like parts in each of the sections 3 and 5.

Each section 3 or 5 has three main silencing components in it. The first of these is a spit chamber (high frequencing silencing) assembly 7; the second or intermediate silencing component 9 is a broad banded tuning chamber that is also designed to attenuate a selected frequency; and the third and final component is a narrow banded tuning chamber assembly 11 which also preferably includes a modified spit chamber.

The spit chamber assembly 7 is connected to the exhaust manifold outlet pipe 13 of the engine 1 by means of a laminated pipe section 15 (FIGURE 2) which is formed from an inside and outside pipe telescoped together in a loose fit and preferably having a total wall thickness of about .084". They are provided with a flange 17 which serves as a means for connecting the exhaust system to the pipe 13 in a clamped and gasketed joint 19. The laminated pipe section 15 can be bent to a contour to suit the automobile. It is a sound deadening component and acts to remove pipe ring and ping. The inner diameter of the pipe section 15 is preferably about 2" and this same diameter is preferably the minimum inner diameter (the diameter of the gas passage) throughout the entire section 3 or 5. It will be seen subsequently that there is a straight through gas passage of this diameter and therefore a minimum back pressure is imposed upon the engine.

The spit chamber assembly 7 comprises an outer shell 21 which is swaged down at its opposite ends so as to provide an inlet bushing section 23 and an outlet bushing section 25. The laminated pipe section 15 fits inside of the inlet bushing 23 and is rigidly secured to it. Preferably arc welding is used to penetrate through to the inner layer of the laminated pipe. The laminated pipe section terminates within the bushing 23 and immediately adjacent to it is the inlet end of the louvered pipe 2? which has its outlet end seated in a support section 31 formed in the housing 21 immediately adjacent and upstream to the outlet bushing 25. The conduit 29 is of uniform diameter throughout its length and has a slip fit at one end in the bushing 23 to provide for differential expansion due to heat, the conduit 29 being heated to a higher temperature than the chamber material 21. The spit chamber shell 21 is preferably about /2" larger in diameter than the louver tube 29 and it is pinched down at four sections, as seen at 33, 35, 37, and 39. As seen in FIG- URE 2A, four sections of the larger outer shell 21 are pinched together in U-shaped bites 41 so that the shell is reduced to a contact fit on the inner tube 29 at the four sections 33, 35, 37, and 39 though noiseless relative longitudinal movement due to differential expansion is permitted. The pinched sections, along with the reduced end sections 23 and 3 1 of the shell 21, divide the interior of the shell 21 into five annular chambers 43, 45, 47, 49, and 51 (going downstream) surrounding the center tube 29. The chambers are of three different lengths. The chamber 43 and the chamber 1 are preferably the longest (about 4.94); the chambers 47 and 49 are preferably the shortest (about 3.82 in length); and the chamber 45 is intermediate in length (about 4"). The inner tube 2 9 is formed with banks B of louvers in each of the chambers and these are preferably substantially round stamped louvers 53 that are formed in the wall of the tube 29 when it is originally fiat-stock and prior to rolling it up into the tube, and these have openings 55 through which the interior of the tube can communicate with the respective chambers 43-51. The particular configuration of the louvers is shown double size and to scale in FIG- URES 3 and 4 and it is desirable to use this shape for best results. The louvers are formed in rows which extend all the way around the tube 29 and the banks of louvers for chambers 43 and 51 preferably contain fewer rows (preferably 11 rows) while the banks of louvers for the chambers 45, 47, and 49 preferably contain m re rows of louvers (preferably 13). Thus, there is a smaller area of opening into the larger volume end chambers 43 and 5-1.

The chambers 43-5 1 remove or attenuate high frequency chink, spit, scratch, and hashy noises and tend to smooth out the exhaust system sound. By making the chambers of slightly different volumes and the banks B of slightly different total louver area openings, a wider spectrum of high frequency sound can be attenuated. Chambers 43 and 511 Will be most effective on slightly lower frequency noises than the chamber 45 and this in turn is more effective on lower frequencies than the two chambers 47 and 49. The total length of the spit chamber assembly 7 is approximately 26".

A connecting pipe 61 is telescoped with the outlet bushings of the shell 21 and welded to it, and the other end of the pipe 61 fits in and is clamped to the inlet bushing 65 of the intermediate mufller 9 by means of the clamp 67.

Referring to FIGURES 5-6, the silencing component 9 has an outer shell 71 which is made of two layers of metal (preferably a .030 outer shell and a .018 inner shell) which are interlocked together and interlocked at their ends with the ends headers 73 and 75. The double layer shell construction is used since high energy sound Waves impinge upon the shell in the unit 9 and the lami nated structure will tend to deaden the resulting impact and eliminate sound resulting from it. This also provides for the inner layer to be made of higher quality material to resist acid corrosion while the outer surface is less expensive material to protect against the less severe salt corrosion, e.g., stainless steel inside and aluminized steel outside.

The inlet bushing 65 extends through and is spotwelded to an inturned annular flange 77 on the inlet header 73. An inner louver tube 79 has a slip fit inside of the reduced inner end of the inlet bushing 65 to allow for differential expansion. At the outlet end, a right angle pipe section 81 has its upstream end 82 adapted to act as the outlet bushing for the mufller 9 and it extends through an inwardly disposed annular flange 83 on the outlet header and is spotwelded to it as well as to the downstream end of the louver tube 79, spotwelds being indicated by the small xs throughout the drawings.

As indicated in FIGURE. 6, the shell 71 is preferably of a rounded rectangular section and is preferably about 4% maximum width and 3% minimum width. Round louvers 85 of the type shown in FIGURES 3 and 4 are formed in rows extending along the full length of the center louver tube 79, there preferably being about rows of such louvers spaced along the length of the tube. A drain hole 91 may be formed in the outlet header 75, as seen in FIGURE 5. This will permit condensate accumulating on the bottom of the shell 71 to drain out of the muffler but the hole is small enough so that there is no adverse acoustic effect.

The unit 9 is preferably about 20 long.

The tuning chamber 9 will attenuate certain selected low frequencies or notes, intermediate roughness, and a broad band of high frequency noises. It will prevent the buildup of high acoustic pressure levels excited by ccincidence between engine firing frequencies and pipe resonant frequencies. The insertion of the unit 9 into the system causes an acoustical interaction with the other elements to shift the standing wave pattern of the resonance frequencies of the system from the position that would occur if the system were devoid of the unit 9. That is, the insertion of the unit 9 change-s the acoustic length of the pipe sections and rearranges the standing wave pattern between the intermediate unit and the natural discharge end of the exhaust system from the pattern that would occur if a straight length of pipe were present in place of the unit 9. The insertion of the unit 11 into the system similarly shifts resonant frequencies and rearranges the standing wave patterns from the condition that would occur if the unit 11 were not present in the system and was replaced by a straight length of pipe section. The net effect is such that the exhaust system resonance frequencies exist at slightly higher values which are somewhat easier to attenuate than would exist if either one or both of the units 9 and 11 were not present in the system at the specific respective location. The unit 9 is located as closely as possible to the anti-node of the 3rd harmonic of the fundamental frequency of the complete section 3 or 5 and is tuned to attenuate this order frequency.

As seen in FIGURE 1, the outlet section 81 of the tuning chamber 9 is clamped by clamps 93 to a curved pipe section 95, the sections 81 and 95 providing a kickup to clear the rear axle of the vehicle. The downstream end of the section 95 extends inside of the inlet bushing 97 of the unit 11 and is rigidly secured to it by a clamp 99. The unit 11 has a single layer outer shell which is preferably about 16%" in overall length. Its cross-sectional shape is as shown in FIGURE 8 which is the same as that of the unit 9 and its cross-sectional dimensions are preferably the same, that is, 3%" x 4%". The shell 101 of the unit 11 has an inlet header 103 with an outwardly extending flanged neck 105 that is fitted around the inlet bushing end 97. Bushing 97 is the inlet end of an inner shell 107 that extends to a point about 2%" from the outlet header 109 of the shell 101. Fitted inside and spotwelded to the inside of the inlet bushing 97 of the inner shell 107 is an inner louver tube 111 and it extends the remaining length of the housing 101 and fits inside and is spotwelded to a combination bushing and tailpipe 113 which, in turn and conjointly with the tube 111, is spotwelded to an inturned flange 115 formed on the outlet header 109. The inner shell 107 is preferably about 2%" in diameter (similar to the spit chamber assembly 7) and defines an annular chamber 117 around the tube 111 which is about 12 /s" long. The space between the shell 101 and the inner shell 107 forms a second and larger volume chamber 119. A bank of fine flat louvers 121 of the shape shown, double-sized and to scale in FIGURES 9 and 10, are formed in the wall of the shell 111 along a portion only of its upstream length, preferably about 6.9, and the remainder, as seen at 123, is not perforated. At the downstream end of the shell 107, its opposite sides are deformedv into contact with the tube 111 and spotwelded to it as seen at 125. However, the sections of the end of the shell 107 between the portions 125 are open and form channel-like outlet passages 127 which communicate the chamber 117 with the chamber 119. The shell 107 therefore acts as a tuning tube or shell for the chamber 119 and these can be tuned to take out the objectionable notes and frequencies in the system. By having the short length of the tailpipe section 113 downstream of unit 11, the unit 11 is placed away from the node at the end of the system. The unit 9 is preferably placed as close as possible to an anti-node of the 3rd harmonic of the fundamental frequency of the complete system and coacts with the other components to determine the location of the 5th harmonic for the entire section 3 or 5. The unit 11 is tuned to attenuate this 5th harmonic. The channels 127 of the shell 107 around the blank space 123 act in particular as tuning tubes to make the unit 11 function as a Helmholtz resonator. Additionally, the shell 107, because of the louvers 121, can act through chamber 117 as a modified type of spit chamber to remove some of the harshness and high frequency sounds.

In operation, it is apparent that the gas which is discharged from one bank of four cylinders in the engine 1 will pass through the exhaust line 3 while the exhaust gas from the other side of V8 engine will pass through the exhaust line 5. In each of the sections the gas will be subjected to similar silencing action. Thus, the high frequency noises and roughness will be attenuated primarily in the spit chamber assembly 7. However, there may also be some high frequency attenuation in the unit 9, as well as in the chamber 117 of unit 11. Intermediate frequencies will be removed principally in the intermediate unit 9. The last unit 11, with the tuning shell construction, is well adapted to handle the lower frequencies.

The spit chamber assembly 7 is placed at a convenient location in the system, preferably upstream of units 9 and 11, so that it can smooth out overall roughness to some extent. It is desirable to place the midpoint of unit 9 as close as possible to an anti-node of the most troublesome frequency in the system, usually the 3rd order. As indicated before, the unit 9 shifts the critical frequencies from the pattern that would exist if the unit 9 were not present in the system and, in elfect, appears to permit the formation of a new standing wave having one end at the unit 9 and its other end at the end of the respective section 3 or 5. The critical frequency exists at a higher value than would occur if the unit 9 were not present in the system but the relatively broad band effect of the unit 9 permits effective attenuation of the new frequency, which is the 3rd harmonic of the fundamental frequency of the entire system.

In one commercially acceptable application for which the present exhaust system is designed the length of each section 3 and 5 is 200". Taking into account physical restrictions on optimum placement the units 7 are placed so that mid-chambers 47 are located 40" from the inlet end of each section; units 9 are placed so that the midpoints are located at about 92 inches from the inlet end; and units 11 are placed so that the midpoint of louver banks 121 are located at about 180 inches from the inlet end.

The position of the silencing components in the system is very important for optimum silencing. The most objectionable frequencies (i.e., frequencies to be silenced) can be measured by instruments in each proposed application and their wave length calculated in accordance with known acoustic theory. From this the distances of the anti-nodes of the objectionable frequencies from the discharge ends of the sections 3 and 5 can be determined and the tuning chambers 9 and 11 located as closely as physical limitations permit to them, that is the midpoint of louver banks 85 and 121 are located as closely as possible to the anti-nodes. Since the anti-nodes are at quarter wave length positions, the tuning chambers 9 and 11 are preferably located as closely as possible to nXquarter wave length from end of pipe positions where n is an odd integer.

In another satisfactory application of the invention, the length of sections 3 and 5 was 200". The objectionable frequencies were the third mode of 76 cycles, the fifth of 127 cycles, based on a fundamental pipe resonant frequency of approximately 25.4 cycles. The inlet end of narrow banded tuner 11 because of physical limitations was positioned about 25 inches from the discharge end, i.e., at about 175 inches from the inlet end and the unit was tuned to attenuate the 5th order (127 cycles). The unit 11 interacted with the other elements of the system to increase the fundamental frequency of the system which would exist if the unit 11 were not present to about 29 cycles, the third to about 87 cycles, and the fifth to about 145 cycles. This caused the anti-nodes or maximum acoustic pressure points of the third and fifth modes in the system to occur at the point where the unit 9 was placed so that it could more readily attenuate both resultant frequencies in conjunction with the unit 11. The resultant position being at about inches from the inlet to the midpoint of unit 9. The unit 11 attenuated the resultant frequencies when interacting with the unit 9 based on a wave length corresponding to the distance of the unit 9 g from the end of the section 3 or 5.

It will be seen that units 9 and 11 take out objectionable pipe resonant frequencies that are created by the pulsating exhaust gases. Unit 7 helps to smooth out the pulsations and removes noise in the gases from the engine, especially noises of 500 cycles and above, but does not remove major pipe resonance sound as do units 9 and 11. The relatively short sections of connecting pipe interconnecting the engine and units 7, 9 and 11 minimize the intensity of vibration and increase the effectiveness of the silencing components. From the design standpoint it has been noted that advantages are obtained by putting the narrow banded tuning chamber 11 at the 5th order antinode closest to the discharge end of the section 3 and 5 but it is within the broad purview of the invention to place it as close as possible to a different 5th order anti-node closer to the upstream end of the system. For example, good silencing has been obtained by reversing the positions of units 7 and 11 since this put the unit 11 adjacent the first anti-node of the 5th mode and had the additional advantage of locating volume or expansion chamber at an upstream point in the system.

It is noted that the laminated pipe section 15 and the laminated shell on the unit 9 will remove the ping or ring and help in the overall sound attenuation by deadening the exhaust system. While the pressure pulses of gas passing down the pipe can expand radially through the various louvers, it is apparent that there is no appreciable back pressure imposed on the system by the exhaust line itself since it is wide open internally from end to end.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A tuning chamber comprising a single ply outer shell having inlet and outlet headers, an inner shell including a reduced end section extending through the inlet header and forming an inlet bushing, a center tube mounted at one end in said inlet bushing and extending the length of the shell to the outlet header, an outlet pipe extending through said outlet header and acting as an outlet bushing, said center tube being mounted in said outlet bushing, said inner shell being spaced from the wall of said center tube except at said upstream end and inlet bushing portion and forming a chamber around said center tube,

the downstream end of said inner shell being reduced in diameter and secured to said center tube but also being open at the end to communicate said chamber between said inner shell and said tube with the chamber between said inner shell and the outer shell, said center tube having a louver bank comprising rows of fine flat louvers opening into the chamber between said inner shell and said center tube, said bank of louvers terminating a substantial distance upstream of the end of said inner shell whereby the chamber portion between the bank and the downstream end opening of said inner shell comprises a tuning tube for the chamber between the inner shell and the outer shell, the portion of said chamber between the inner shell and the center tube upstream of said tuning passage comprising a modified spit chamber for attenuating medium and high frequencies.

2. A tuning chamber as set forth in claim 1 in combination with an exhaust system for an internal combustion engine, said system comprising a first silencing unit for attenuating high frequency sounds, a second silencing unit for silencing a broad range of intermediate frequency sounds, said tuning chamber comprising the third silencing unit of said system, and conduit means interconnecting 8 the discharge end of said first silencing unit with the inlet end of said second silencing unit and connecting the discharge end of said second silencing unit with the inlet bushing of said tuning chamber.

References Cited UNITED STATES PATENTS 2,043,030 6/1936 Bourne 18l-59 2,176,615 10/1939 Starkweather et al. 181-48 2,277,132 3/1942 Moss 181-54 2,297,046 9/1942 Bourne 181-48 2,332,543 10/1943 Wilson 181---48 2,580,564 1/1952 Ludlow 18148 2,930,440 3/1960 Fetzer et al. 181--35.2 2,936,041 5/1960 Sharp et al. 181--35.2 3,036,654 5/1962 Powers 181--35.2

FOREIGN PATENTS 1,351,921 12/1963 France.

742,529 12/ 1955 Great Britain.

R OBERT S. WARD, 111., Primary Examiner. 

